The mission for the Kepler spacecraft is to find planets -- particularly planets that may be similar to Earth -- by watching them pass in front of their parent stars -- events called transits. And so far, it's found more than a dozen planets that way, and evidence of more than 1200 more. Astronomers are using telescopes on the ground to see which of those really are planets.

But as NASA scientist Jack Lissauer explains, Kepler also has a second way to see planets.

LISSAUER: With Earth-like planets, the only way Kepler can possibly detect them is when they are transiting in front of their star. However, with Jupiter-size planets that orbit close to the stars, we can see variations in the light that is reflected by those Jupiters. And in fact, we can also see when these close-in Jupiter-sized planets are hidden behind the star because then the reflected light disappears altogether.

Follow-up observations can not only detect these kinds of planets, but reveal some details about them. Texas astronomer Bill Cochran is a member of the Kepler team:

COCHRAN: When the planet is outside of transit, we can actually sometimes see the infrared radiation that is given off by the planet itself. So we can get a temperature for the planet, and thus infer a lot about the atmospheric conditions that exist on that particular planet.

So Kepler should provide not just a list of planets in other star systems, but dossiers about those planets as well.

Script by Damond Benningfield, Copyright 2011

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